Physical
Quantities (Electrical), Symbols and Units |
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|
Quantity |
Symbol |
Unit |
Abbreviation
of Unit after Numerical Value |
|
Force |
F |
newton |
N |
|
Work or Energy |
W |
joule or newton metre |
J or Nm |
|
Torque |
T |
newton metre |
Nm |
|
Power |
P |
watt |
W |
|
Time |
t |
second |
s |
|
Angular Velocity |
w |
radians per second |
rad/s |
|
Speed |
N |
revolutions per minute |
rev/min (sometimes r.p.m.) |
|
n |
revolutions per second |
rev/s (sometimes r.p.s.) |
|
|
Electric Charge |
Q |
coulomb |
C |
|
Potential Difference (p.d.) |
V |
volt |
V |
|
Electromotive force (e.m.f.) |
E |
volt |
V |
|
Current |
I |
ampere |
A |
|
Resistance |
R |
ohm |
W |
|
Resistivity (specific resistance) |
r (rho) |
ohm metre |
Wm |
|
Conductance |
G |
siemens |
S |
|
Magnetomotive force (m.m.f.) |
F |
ampere-turn |
At |
|
Magnetic field strength |
H |
ampere-turn per metre or ampere per metre |
At/m or A/m |
|
Magnetic flux |
f (phi) |
weber |
Wb |
|
Magnetic flux density |
B |
tesla |
T |
|
Reluctance |
S |
ampere-turn or ampere per weber |
At/Wb or A/Wb |
|
Absolute permeability of free space |
m0 (mu) |
henry per metre |
H/m |
|
Absolute permeability |
m |
henry per metre |
H/m |
|
Relative permeability |
mr |
- |
- |
|
Self inductance |
L |
henry |
H |
|
Mutual inductance |
M |
henry |
H |
|
Reactance |
X |
ohm |
W |
|
Impedance |
Z |
ohm |
W |
|
Frequency |
F |
hertz |
Hz |
|
Capacitance |
C |
farad |
F |
|
Absolute permittivity of free space |
e0 (epsilon) |
farad per metre |
F/m |
|
Absolute permittivity |
e |
farad per metre |
F/m |
|
Relative permittivity (dielectric constant, specific
inductive capacity) |
er |
- |
- |
|
Electric field strength, electric force |
- |
volts per metre |
V/m |
|
Electric flux |
Y
(psi) |
coulomb |
C |
|
Electric flux density, electric displacement |
D |
coulomb per square metre |
C/m2 |
|
Active power |
P |
watt |
W |
|
Reactive power |
Q |
volt ampere reactive |
VAr |
|
Apparent power |
S |
volt ampere |
VA |
|
Phase difference |
f
(phi) |
degree |
0 |
|
Power factor (p.f.) |
|
- |
- |
|
Conversion
into SI Units |
||
|
To
Convert |
Multiply
by |
Conversely
Multiply by |
|
Distance |
||
|
inches – millimetres |
25.400 |
0.0394 |
|
inches –
centimetres |
2.540 |
0.3937 |
|
feet – metres |
0.3048
|
3.2808 |
|
yards – metres |
0.914 |
1.094 |
|
miles –
kilometres |
1.6093 |
0.621 |
|
nautical miles –
kilometres |
1.852 |
0.539 |
|
nautical miles –
metres |
1852 |
0.0005399 |
|
fathom – m |
1.8228 |
0.5487 |
|
micron – metre |
10-6 |
106 |
|
Area |
||
|
square inches –
square millimetres |
645.16 |
15.50 |
|
square inches –
square centimetres |
6.4516 |
0.1550 |
|
square feet –
square metres |
0.0929 |
10.764 |
|
Volume |
||
|
cubic inches –
cubic centimetres |
16.387 |
0.061 |
|
cubic feet –
cubic metres |
0.02832 |
35.315 |
|
gallons – litres
(1 litre = 1 cubic decimetre) |
4.546 |
0.220 |
|
gallons – m3 |
4.546
x 10-3 |
219.9 |
|
litre – m3 |
10-3 |
103 |
|
pint – m3 |
0.568 x 10-3 |
1760.5 |
|
quart – m3 |
1.136
x 10-3 |
879.9 |
|
ocean tons –
cubic metres |
1.132 |
0.883 |
|
gallons/minute –
m3/h |
0.273 |
3.666 |
|
Velocity |
||
|
feet/s – m/s |
0.3048 |
3.281 |
|
miles/h – km/h |
1.609 |
0.6215 |
|
knots (nautical
mile per hour) – m/s |
0.5144 |
1.943 |
|
mile/h – m/s |
0.447
|
|
|
Mass |
||
|
gram – kg |
10-3 |
103 |
|
pound (lbm) – kg
|
0.45359237 |
2.2046 |
|
slug – kg |
14.59 |
0.0685 |
|
ton – kg |
1016 |
0.9842 x 10-3 |
|
tonne (metric) –
kg |
103 |
10-3 |
|
tons – tonnes |
1.016 |
0.984 |
|
Pressure |
||
|
tons/in2
– kg/mm2 |
1.575 |
6.635 |
|
dyne/cm2
– N/m2 |
0.1 |
10 |
|
kgf/ cm2
– kN/m2 |
98.07 |
0.0102 |
|
p.s.i. (lbf /
inch2) – kg/mm2 |
0.070 |
14.223
|
|
p.s.i. (lbf /
inch2) – kN/m2 |
6.89476 |
0.145 |
|
inches of water
– N/m2 |
249.5 |
4.008 x 10-3 |
|
feet of water –
kN/m2 |
2.989 |
0.3345 |
|
inches of Hg –
kN/m2 |
3.386 |
0.2953 |
|
mm of Hg – kN/m2 |
0.1333 |
7.502 |
|
torr – mm of
Hg |
1 |
1 |
|
Pascal (Pa) –
N/m2 |
1 |
1 |
|
bar – kN/m2 |
100 |
0.01 |
|
atm – kN/m2 |
101.333 |
98.69 x 10-3
|
|
Conversion
into SI Units |
||
|
To
Convert |
Multiply
by |
Conversely
Multiply by |
|
Density |
||
|
gram/cm3
– kg/m3 |
103 |
10-3 |
|
pound/foot3
– kg/m3 |
16.02 |
0.0624 |
|
pound/inch3
– kg/m3 |
27.679 x 109 |
36.123 x 10-12 |
|
slug/foot3 –
kg/m3 |
515.4 |
1.94 x 10-3 |
|
Force |
||
|
dyne – N |
10-5 |
105 |
|
kgf – N |
9.807 |
0.102 |
|
lbf – N |
4.44822 |
0.2248 |
|
Energy |
||
|
Erg – J |
10-7 |
107 |
|
calorie – J |
4. 1868 |
0.2388 |
|
foot-pound – J |
1.356 |
0.7375 |
|
Btu – kJ |
1.05506 |
0.9478 |
|
Power |
||
|
erg/second – W =
Nm/s = J/s |
10-7 |
107 |
|
foot-pound/second
– W |
1.356 |
0.7375 |
|
horsepower – kW |
0.7457 |
1.341 |
|
horsepower – W |
745.700 |
1341 |
|
horsepower
(metric) – kW |
0.7355 |
1.360 |
|
British h.p.
(745.7 w) – metric h.p. (735.5w) |
1.014 |
0.986 |
|
Discharge |
||
|
cusecs (ft3/s)
– m3/s |
0.02832 |
35.33 |
|
gpm (gallons /
min) – m3/s |
3.0758 x 103 |
0.3251 x 10-3 |
|
litre/s – m3/s |
10-3 |
103 |
|
pound/sec – kg/s |
0.4536 |
2.204 |
|
Prefixes,
Symbols, Multiples and Sub-multiples of the S.I. System |
||
|
Prefix |
Symbol |
Units
Multiplying Factor |
|
tetra |
T |
1012 |
|
giga |
G |
109 |
|
mega |
M |
106 |
|
kilo |
k |
103 |
|
hecto |
h |
102 |
|
deca |
da |
101 |
|
deci |
d |
10-1 |
|
centi |
c |
10-2 |
|
milli |
m |
10-3 |
|
micro |
m |
10-6 |
|
nano |
n |
10-9 |
|
pico |
p |
10-12 |